body {
    margin: 0;
    padding: 0;
}

.header {
    height: 80px;
    background-color: blue;
}

.container {
    display: flex;
    height: calc(100vh - 80px);
}

.sidebar {
    width: 200px;
    background-color: gray;
}

.main-content {
    flex: 1;
}